Egyptian authorities have arrested seven people who allegedly raised a rainbow flag at a concert held in Cairo.

Key points:

Homosexuality is not explicitly prohibited under Egyptian law

Authorities instead prosecute people under alternative charges including inciting immorality

The Lebanese band has since been banned from performing in Egypt

The flag raising was a rare sign of support for highly marginalised homosexuals in conservative Egypt.

It took place at a concert held on Friday by popular Lebanese indie rock band Mashrou' Leila, whose lead singer is openly gay.

The band has subsequently been banned from performing in Egypt by the country's official musicians union.

The seven were arrested on Monday and charged with "inciting immorality," security officials said, adding that the Supreme State Security Prosecution acted after authorities discovered the seven had "raised the flag of homosexuals".

The officials spoke to the Associated Press on condition of anonymity because they were not authorised to talk to journalists.

Homosexuality is highly taboo in Egypt among both majority Muslims and the Christian minority, but it is not explicitly prohibited by law.